[+cc Joerg, Alex] Hi Kelly, On Tue, Feb 23, 2016 at 03:52:13PM +0000, Zytaruk, Kelly wrote: > As per our offline discussions I have created Bugzilla #112941 for > the SRIOV issue. https://bugzilla.kernel.org/show_bug.cgi?id=112941 > When trying to enable SRIOV on AMD GPU after doing a previous enable > / disable sequence the following warning is shown in dmesg. I > suspect that there might be something missing from the cleanup on > the disable. > > I had a quick look at the code and it is checking for something in > the iommu, something to do with being attached to a domain. I am > not familiar with this code yet (what does it mean to be attached to > a domain?) so it might take a little while before I can get the time > to check it out and understand it. > > From a quick glance I notice that during SRIOV enable the function > do_attach() in amd_iommu.c is called but during disable I don't see > a corresponding call to do_detach (...). do_detach(...) is called > in the second enable SRIOV sequence as a cleanup because it thinks > that the iommu is still attached which it shouldn't be (as far as I > understand). > > If the iommu reports that the device is being removed why isn't it > also detached??? Is this by design or an omission? I don't know enough about the IOMMU code to understand this, but maybe the IOMMU experts I copied do. > I see the following in dmesg when I do a disable, note the device is removed. > > [ 131.674066] pci 0000:02:00.0: PME# disabled > [ 131.682191] iommu: Removing device 0000:02:00.0 from group 2 > > Stack trace of warn is shown below. > > [ 368.510742] pci 0000:02:00.2: calling pci_fixup_video+0x0/0xb1 > [ 368.510847] pci 0000:02:00.3: [1002:692f] type 00 class 0x030000 > [ 368.510888] pci 0000:02:00.3: Max Payload Size set to 256 (was 128, max 256) > [ 368.510907] pci 0000:02:00.3: calling quirk_no_pm_reset+0x0/0x1a > [ 368.511005] vgaarb: device added: PCI:0000:02:00.3,decodes=io+mem,owns=none,locks=none > [ 368.511421] ------------[ cut here ]------------ > [ 368.511426] WARNING: CPU: 1 PID: 3390 at drivers/pci/ats.c:85 pci_disable_ats+0x26/0xa4() This warning is because dev->ats_enabled doesn't have the value we expect. I think we only modify ats_enabled in two places. Can you stick a dump_stack() at those two places? Maybe a little more context will make this obvious. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
